Operators use waterflood regulators in side pocket mandrels to regulate what volume of injected fluid can enter a wellbore annulus. Ideally, the regulators control the injected fluid without producing significant pressure variations. A typical waterflood completion 10 illustrated in FIG. 1 has a wellhead 12 atop a casing 14 that passes through a formation. A tubing string 20 positioned in the casing 14 has a number of side pocket mandrels 60 positioned between packers 40. Surrounding the tubing string 20, these packers 40 separate the casing's annulus 16 into multiple isolated zones that can be separately treated.
To conduct a waterflood operation, operators install the waterflood regulators 70 by slickline into the side pocket mandrels 60. Shown in more detail in FIG. 2A, the mandrel 60 has a side pocket 64 in an offset bulge 62 on the mandrel 60. The pocket's upper end has a seating profile 65 for engaging a locking mechanism of the regulator (70) or other tool, while the pocket's other end 67 may be open. Ports 66 in the mandrel's pocket 64 communicate with the surrounding annulus (16) and allow for fluid communication during waterflood, gas lift, or other types of operations. The mandrel 60 may also have an orienting sleeve 61 for facilitating slickline operations and for properly aligning the regulator (70) within the pocket 64. During installation, a tool discriminator (not shown) can be used to guide the regulator (70) into the pocket 64 and deflects larger tools to prevent damage to the regulator (70).
With the completion 10 of FIG. 1 having the regulators 70 installed, operators can proceed with the waterflood operation by injecting fluid (e.g., water or the like) into the tubing string 20. The injected fluid passing down the tubing string 20 must first pass through the waterflood regulators 70 before it can pass into the annulus 16 through the mandrels' ports 66. Once in the annulus 16, the fluid can then pass through the casing's perforations 15 and interact with the surrounding formation.
In use, the installed regulators 70 allow fluid to flow from the tubing string 20 to the annulus 16 through the mandrels' ports 66 and restrict fluid flow in the reverse direction. In other words, the regulators 70 act as one-way valves and regulate the volume of water that can pass from the tubing string 20 to the annulus 16. Each of the regulators 70 operate independently of one another and separately control the volume of fluid that can enter the adjacent isolated zone. In this way, each of the regulators 70 can compensate for differential pressure changes in each zone and can provide a constant volume of fluid for each zone.
In a new waterflood completion, operators typically first set the packers 40 and test their pressure containment before performing the waterflood operation. Because the mandrels 60 have side ports 66 and the regulators 70 control fluid flow into the annulus 16, operators first install dummy valves in each of the mandrels 60 to isolate flow between the tubing string 20 and the casing annulus 16. For example, FIG. 2B shows a dummy valve 30 installed in the mandrel's pocket 64 using a slickline (not shown) and latch 34. When installed, the dummy valve 30 does not actually operate as a valve. Instead, the dummy valve 30 has a closed or solid body, and packings 32 on the outside of the dummy valve 30 straddle and pack off the ports 66 to the annulus 16 to prevent fluid flow into the annulus 16. Once the dummy valves 30 have been installed in the mandrels 60 of the completion 10 as in FIG. 1, operators can hydraulically set the packers 40 and can also test that the packers 40 are correctly set and do not leak by pumping fluid down the tubing string 20 without having the fluid pass to the annulus 16. In this way, the dummy valve 30 facilitates setting and testing of the packers 40.
After setting and/or testing the packers 40, operators must then retrieve the dummy valves 30 from the mandrels 60 using slickline operations. Then, as shown in FIG. 2C, operators install the waterflood regulators 70 into the mandrel's side pockets 64 with additional slickline operations. One typical example for the waterflood regulator 70 is the RWF-2R series regulator available from Weatherford/Lamb, Inc.—the Assignee of the present disclosure. These regulators 70 also have a latch 74 and have packings 72 that straddle and packoff the mandrel's ports 66.
In use, fluid in the mandrel 60 can pass into a ported nose 78 on the regulator 70. Entering the nose 78, the fluid flow can route up the center of the regulator 70 and can exit ports 76 in the regulator's side to communicate through the mandrel's ports 66. Internally, the regulator 70 has a reverse flow check valve (not shown) to regulate the flow inside the regulator 70 and to prevent back flow from the annulus 16 into the tubing string 20.
Unfortunately, the process of first installing and then retrieving the dummy valves 30 as in FIG. 2B and then installing the regulators 70 as in FIG. 2C takes a considerable amount of time to perform, especially when the well has multiple isolated zones. In addition, the multiple installations and retrievals increase the risk of losing tools in the wellbore, which can be detrimental to operations.
In some completions, operators install special dummy valves (referred to as equalizing dummy valves) that allow operators to equalize pressures between the tubing string 20 and the annulus 16 once testing has been completed. With these dummy valves, operators run a slickline down the tubing string 20 to remove a prong on the dummy valve while it is still installed in the mandrel 60. With the prong removed, operators can circulate fluid freely through the dummy valve so that the valve essentially operates as a circulator to equalize the casing and tubing pressures. Even with these equalizing dummy valves, however, operators must still perform additional slickline operations to perform a waterflood operation by pulling the equalizing valves from the mandrel 60 and subsequently installing the regulators 70 in the mandrels 60.
What is needed is a way to simplify the installation process of a waterflood completion and to reduce the risk of losing tools in the wellbore in the process.